Long-term isolation at a low effective population size greatly reduced genetic diversity in Gulf of California fin whales

Vania E. Rivera-León,Wensi Hao,Per J. Palsbøll,Tom Oosting,Sally Mizroch,Jorge Urbán,Martine Bérubé,Robert L. Brownell

doi:10.1038/s41598-019-48700-5

Abstract

The Gulf of California, Mexico is home to many cetacean species, including a presumed resident population of fin whales, Balaenoptera physalus. Past studies reported very low levels of genetic diversity among Gulf of California fin whales and a significant level of genetic differentiation from con-specifics in the eastern North Pacific. The aim of the present study was to assess the degree and timing of the isolation of Gulf of California fin whales in a population genetic analysis of 18 nuclear microsatellite genotypes from 402 samples and 565 mitochondrial control region DNA sequences (including mitochondrial sequences retrieved from NCBI). The analyses revealed that the Gulf of California fin whale population was founded ~2.3 thousand years ago and has since remained at a low effective population size (~360) and isolated from the eastern North Pacific (Nem between 0.89–1.4). The low effective population size and high degree of isolation implied that Gulf of California fin whales are vulnerable to the negative effects of genetic drift, human-caused mortality and habitat change.

Highlights

Population genetic data hold the potential to provide insights into the basis of genetic variation in natural populations[1], which in turn is a function of past and present effective population sizes, migration rates, selection, and mutation rates
The analyses in this study revealed that the Gulf of California fin whale population was founded approximately
Our results supported the notion that the establishment of the Gulf of California fin whale population was not a recent phenomenon

Summary

Introduction

Population genetic data hold the potential to provide insights into the basis of genetic variation in natural populations[1], which in turn is a function of past and present effective population sizes, migration rates, selection, and mutation rates. Baleen whales are commonly observed around the Midriff Islands and in the Canal de Ballenas between the east coast of the Baja California Peninsula and Isla Angel de la Guarda[21,22,23]. Since the 1980s, regular surveys aimed at baleen whales in the Gulf of California have been conducted in the waters off the Midriff Islands, in particular Canal de Ballenas[21,23,28,29,30] Fin whales, and their vocalizations have been recorded throughout the year in the Gulf of California and appear most abundant in the Upper Gulf[21,23,31,32]. Some occasional tempo-spatial overlap was noted in fin whale calls recorded in the Gulf of California and off Southern California, indicating the possibility of some connectivity between these two areas[39]

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Conclusion